Mallow carrier board Verdin-Am62 LVDS screen flickering

Technical Support
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1

Hi,

We are experiencing a problem with our display touch panel that is connected to a Verdin AM62 SoM and a mallow carrier board through native LVDS which flickers constantly. We tried fixing it by changing the device tree panel timings according to the touch panel datasheet. We also measured the DCLK frequency but no matter what we set in the device tree it always showed a lower frequency than the one that was set (e.g. the .dts file had DCLK freq set to ~50MHz and the measurement showed ~20MHz). We also noticed that these problems do not occur when connecting the display through a DSI-to-LVDS connector (on Dahlia carrier board).

I’m sending you the device tree that we use for the native LVDS interface:
verdin-am62_panel-cap-touch-5inch-lvds_ilitek-inverted_overlay.dts (4.4 KB)

Tdx Info:

Software summary
------------------------------------------------------------
Bootloader:               U-Boot
Kernel version:           6.6.84-7.3.0-devel-g9d1f86864908 #1-Torizon SMP PREEMPT Thu May 29 10:29:09 UTC 2025
Kernel command line:      root=LABEL=otaroot rootfstype=ext4 quiet logo.nologo vt.global_cursor_default=0 plymouth.ignore-serial-consoles splash fbcon=map:3 ostree=/ostree/boot.1/torizon/d4be0d9fcde4ef75b9f04279ca846b85dd668cde5b3c8a8a92e3bd87f973ba02/0
Distro name:              NAME="Torizon OS"
Distro version:           VERSION_ID=7.3.0-devel-202506-build.9
Distro variant:           VARIANT="Docker"
Hostname:                 verdin-am62-15380640
------------------------------------------------------------

Hardware info
------------------------------------------------------------
HW model:                 Toradex Verdin AM62 WB on Mallow Board
Toradex version:          0076 V1.1C
Serial number:            15380640
Processor arch:           aarch64
------------------------------------------------------------
2

Hi, I’m the Toradex AI Assistant.

I might make mistakes or occasionally get you wrong. Our support team will step in if needed.

Looking at your LVDS display issue with the Verdin AM62 SoM on the Mallow carrier board, I can help you troubleshoot the flickering and clock frequency problems you’re experiencing.

Root Cause Analysis

Based on the available documentation and your description, there are several potential causes for the flickering and clock frequency discrepancies:

1. Display Control Signals

The fact that your display works properly with the DSI-to-LVDS adapter but not with native LVDS suggests that control signals may not be properly configured (1). Native LVDS displays often require specific power-on sequences and control signals (such as RESET_N, DISPLAY_ON, or enable signals) that need to be properly managed through GPIO pins (1).

2. Data Mapping Configuration

Display flickering can be caused by incorrect data mapping settings (2). The data mapping determines how the RGB data is transmitted over the LVDS interface, and using the wrong mapping can cause visual artifacts (2).

3. Clock Domain Issues

The clock frequency discrepancy you’re observing (50MHz set vs 20MHz measured) indicates a potential issue with the clock configuration or pixel clock generation in the native LVDS path.

Troubleshooting Steps

Step 1: Verify Control Signals

Check if your display requires control signals and ensure they are properly configured as GPIOs in your device tree overlay (1). You may need to add GPIO control for signals like:

  • Display enable/power
  • Reset signals
  • Backlight control

Step 2: Review Data Mapping

Verify that your data-mapping property matches your display’s requirements (2). Common options include:

  • "jeida-18" or "jeida-24"
  • "spwg"
  • "vesa-24"

Step 3: Check Panel Timing Parameters

Ensure all timing parameters in your device tree match your display datasheet exactly (3). Pay particular attention to:

  • clock-frequency
  • hactive, vactive
  • hsync-len, vsync-len
  • Front and back porch values

Step 4: Validate Device Tree Structure

Your device tree overlay should follow the proper structure for native LVDS on Verdin AM62 (4). The overlay should configure the OLDI (LVDS) interface correctly and ensure proper port connections.

Device Tree Configuration Guidelines

When creating your device tree overlay, ensure you’re following the proper device tree structure and syntax (5). The device tree should include:

  1. Panel node with correct compatible string and timing parameters (3)
  2. Proper port connections between the panel and LVDS controller (5)
  3. GPIO configurations for any required control signals (1)
  4. Correct data mapping for your specific display (2)

Next Steps

Since I cannot see the specific content of your uploaded device tree file, I recommend:

  1. Compare with working DSI-to-LVDS configuration - Check what differs between the working DSI-to-LVDS setup and your native LVDS configuration
  2. Verify hardware connections - Ensure all required control signals are properly connected on your Mallow carrier board
  3. Test with reference overlay - Try using a reference LVDS overlay from the available pre-built overlays (4) as a baseline

The clock frequency discrepancy is particularly concerning and suggests a fundamental configuration issue with the LVDS clock domain that needs to be addressed at the device tree level.

Best regards, Toradex AI Assistant.

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3

The issue still persists, I don’t think it’s any of the mentioned above by the AI. Is it just a hardware limitation? Also sorry for my mistake in the top post. The flickering actually occurrs on a 7" LVDS display (Riverdi RVT70HSLNWN00). The 5" display doesn’t really show any flickering due to the low enough frequency of around ~20MHz.

This is the updated 7" Device Tree that we use
verdin-am62_panel-cap-touch-7inch-lvds_ilitek-inverted_overlay.dts (3.6 KB)

4

LVDS Display Limitations on Verdin AM62

Based on the documentation and your updated information about the Riverdi RVT70HSLNWN00 7" LVDS display, there are indeed potential hardware limitations to consider.

Supported LVDS Configuration

According to the Verdin AM62 datasheet, the native LVDS interface has specific characteristics (1):

  • Single channel LVDS interface can support resolutions up to 1920x1080p at 60 frames per second (165MHz pixel clock maximum) (1)
  • For higher resolutions, a second LVDS channel is required (1)
  • The LVDS interface is classified as “module-specific”, meaning it may not be present on other modules or even when present it may not share the same pins (1)

Clock Frequency Limitations

The clock frequency issue you’re experiencing (lower measured frequency than configured) could be related to the LVDS clock generation capabilities. The Verdin AM62 supports LVDS through the Open LVDS Display Interface (OLDI) on the SoC (OLDITX0), providing 8 data lanes (pairs) split into 2 channels (1)(2).

Mallow Carrier Board Compatibility

The Mallow Carrier Board officially supports a limited set of displays (3):

  • Capacitive Touch Display 10.1" LVDS
  • Capacitive Touch Display 10.1" DSI
  • Capacitive Touch Display 7" DSI

Note that the official list does not include native 7" LVDS displays (4). The supported 7" display is DSI-based, not LVDS (5).

Hardware Limitation Assessment

Your observation that the 5" display works at ~20MHz while the 7" display flickers suggests you may be encountering:

  1. Clock domain limitations in the native LVDS implementation for higher pixel clock frequencies required by 7" displays
  2. Signal integrity issues at higher frequencies on the native LVDS interface
  3. Power delivery constraints for higher frequency LVDS operation

Alternative Solution

Since you mentioned the display works properly with DSI-to-LVDS on the Dahlia carrier board, this confirms that:

  • The display itself is functional
  • The DSI interface can provide the required clock frequencies and signal quality
  • The issue is specifically with the native LVDS implementation

Recommendation

Given that:

  • The Mallow carrier board doesn’t officially support 7" LVDS displays (4)
  • Your display works with DSI-to-LVDS conversion (3)
  • The native LVDS shows frequency limitations

Consider using a DSI-to-LVDS adapter on the Mallow carrier board rather than the native LVDS interface. The Mallow board supports DSI displays (4), and you’ve already proven this approach works with your display.

This appears to be a hardware limitation of the native LVDS implementation on the Verdin AM62/Mallow combination for your specific display requirements.

Best regards, Toradex AI Assistant.

Did you like my answer? :+1: :-1:

If I answered your question, please tick the “Solution” checkbox.

For follow-up questions to me, please use @ToradexAI in your post.

5

Hi @daniel.l!

Sorry for the delayed answer.

Were you able to solve the issue? If so, could you please share the solution?

Best regards.

6

Hi, @lucas_az.tx ,

We’ve left the topic for some time now to focus on other things. The behavior however stays the same, the 7" Riverdi display which I provided earlier flickers with the attached verdin-am62_panel-cap-touch-7inch-lvds_ilitek-inverted_overlay.dts (also attached in my previous response). It is visible mostly on bright screens like a gray background.